For tonight's Conversation With Great Minds - I'm joined by one of the country's foremost experts on nuclear security and nuclear nonproliferation. As the president of the global security organization the Ploughshares Fund - Jospeh Cirincione is on the frontline of the fight to prevent the spread of dangerous nuclear weapons. He is also a member of Secretary of State John Kerry's International Security Advisory Board and the Council on Foreign Relations. Before taking his position at the Ploughshares Fund in 2008 - Joseph worked on nonproliferation issues for the U.S. House of Representatives - Center for American Progress - and the Carnegie Center for International Peace. He is the author of a number of books on nuclear weapons policy - including his latest -"Nuclear Nightmares: Securing the World Before It Is Too Late" - a fascinating - and often sobering - look at the reality of modern day nuclear destruction.